Add the cpr-transfer migration mode. Usage:
qemu-system-$arch -machine anon-alloc=memfd ...
start new QEMU with "-incoming -cpr-uri "
Issue commands to old QEMU:
migrate_set_parameter mode cpr-transfer
migrate_set_parameter cpr-uri
migrate -d
The migrate command stops the VM, saves CPR state to uri-2, saves
normal migration state to uri-1, and old QEMU enters the postmigrate
state. The user starts new QEMU on the same host as old QEMU, with the
same arguments as old QEMU, plus the -incoming option. Guest RAM is
preserved in place, albeit with new virtual addresses in new QEMU.
This mode requires a second migration channel, specified by the
cpr-uri migration property on the outgoing side, and by the cpr-uri
QEMU command-line option on the incoming side. The channel must
be a type, such as unix socket, that supports SCM_RIGHTS.
Memory-backend objects must have the share=on attribute, but
memory-backend-epc is not supported. The VM must be started with
the '-machine anon-alloc=memfd' option, which allows anonymous
memory to be transferred in place to the new process. The memfds
are kept open by sending the descriptors to new QEMU via the
cpr-uri, which must support SCM_RIGHTS, and they are mmap'd
in new QEMU.
Signed-off-by: Steve Sistare
---
migration/cpr.c | 9 -
migration/migration.c | 37 +
migration/ram.c | 1 +
migration/vmstate-types.c | 5 +++--
qapi/migration.json | 26 +-
stubs/vmstate.c | 7 +++
6 files changed, 81 insertions(+), 4 deletions(-)
diff --git a/migration/cpr.c b/migration/cpr.c
index 50c130c..7ac01a9 100644
--- a/migration/cpr.c
+++ b/migration/cpr.c
@@ -58,7 +58,7 @@ static const VMStateDescription vmstate_cpr_fd = {
VMSTATE_UINT32(namelen, CprFd),
VMSTATE_VBUFFER_ALLOC_UINT32(name, CprFd, 0, NULL, namelen),
VMSTATE_INT32(id, CprFd),
-VMSTATE_INT32(fd, CprFd),
+VMSTATE_FD(fd, CprFd),
VMSTATE_END_OF_LIST()
}
};
@@ -172,6 +172,8 @@ int cpr_state_save(Error **errp)
if (mode == MIG_MODE_CPR_EXEC) {
f = cpr_exec_output(errp);
+} else if (mode == MIG_MODE_CPR_TRANSFER) {
+f = cpr_transfer_output(migrate_cpr_uri(), errp);
} else {
return 0;
}
@@ -209,6 +211,11 @@ int cpr_state_load(Error **errp)
*/
if (cpr_exec_has_state()) {
f = cpr_exec_input(errp);
+if (cpr_uri) {
+warn_report("ignoring cpr-uri option for migration mode cpr-exec");
+}
+} else if (cpr_uri) {
+f = cpr_transfer_input(cpr_uri, errp);
} else {
return 0;
}
diff --git a/migration/migration.c b/migration/migration.c
index a4a020e..65a36a6 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -77,6 +77,7 @@ static NotifierWithReturnList
migration_state_notifiers[MIG_MODE__MAX] = {
NOTIFIER_ELEM_INIT(migration_state_notifiers, MIG_MODE_NORMAL),
NOTIFIER_ELEM_INIT(migration_state_notifiers, MIG_MODE_CPR_REBOOT),
NOTIFIER_ELEM_INIT(migration_state_notifiers, MIG_MODE_CPR_EXEC),
+NOTIFIER_ELEM_INIT(migration_state_notifiers, MIG_MODE_CPR_TRANSFER),
};
/* Messages sent on the return path from destination to source */
@@ -205,6 +206,12 @@
migration_channels_and_transport_compatible(MigrationAddress *addr,
return false;
}
+if (migrate_mode() == MIG_MODE_CPR_TRANSFER &&
+addr->transport == MIGRATION_ADDRESS_TYPE_FILE) {
+error_setg(errp, "Migration requires streamable transport (eg unix)");
+return false;
+}
+
return true;
}
@@ -1697,6 +1704,7 @@ bool migrate_mode_is_cpr(MigrationState *s)
{
MigMode mode = s->parameters.mode;
return mode == MIG_MODE_CPR_REBOOT ||
+ mode == MIG_MODE_CPR_TRANSFER ||
mode == MIG_MODE_CPR_EXEC;
}
@@ -2038,6 +2046,12 @@ static bool migrate_prepare(MigrationState *s, bool
resume, Error **errp)
return false;
}
+if (migrate_mode() == MIG_MODE_CPR_TRANSFER &&
+!s->parameters.cpr_uri) {
+error_setg(errp, "cpr-transfer mode requires setting cpr-uri");
+return false;
+}
+
if (migration_is_blocked(errp)) {
return false;
}
@@ -2144,6 +2158,29 @@ void qmp_migrate(const char *uri, bool has_channels,
goto out;
}
+/*
+ * For cpr-transfer mode, the target first reads CPR state, which cannot
+ * complete until cpr_state_save above finishes, then the target creates
+ * the migration channel and listens. We must wait for the channel to
+ * be created before connecting to it.
+ *
+ * This implementation of waiting is a hack. It restricts the channel
+ * type, and will loop forever if the target dies. It should be defined
+ * as a main-loop event that calls connect on the back end.
+ */
+if (s->parameters.mode == MIG_MODE_CPR_TRANSFER) {
+Sock
